Fuel Saving Technologies
Lead-acid battery – invented in 1859 by Gaston Plante – has been improved significantly over recent years and, despite being one of the heaviest electrochemical systems, still maintains its position as the number one choice in the automotive industry for starting, lighting and ignition (SLI). Now, bigger challenges await the lead-acid battery.
The Battery Market in the 21st Century
One of the principal reasons that lead-acid batteries maintain popularity is that their cost and recyclability enjoys a significant 10 times cost advantage over new technologies such as lithium-ion. This factor will obviously change as mass production of newer technologies drives down production costs and end user prices. However, for the time being, lead-acid is still the first choice in SLI.
The production of electrical power is governed by two complex chemical reactions between cathode and anode. They deliver a combined voltage of just over 2V per cell or 12V for the six cell configuration used in automotive batteries. As the positive and negative electrodes are made of weak materials, they require support provided by a grid made from a lead alloy. As well as providing physical support for the active materials, the grid also conducts the electrical charge from the electrodes to the outside world.
Over the years many different lead alloys have been developed for the grid, and this technology is often used in marketing batteries to make it appear as if there is a whole new battery technology – calcium-calcium, silver-calcium etc. In truth, however, these are simply process improvements in the development of Plante’s original design that have beneficial effects such as reducing water loss and making the automotive batteries of today maintenance-free and longer lasting than their ancestors.
Concerns over climate change are heavily influencing all aspects of vehicle design including batteries. New technologies, such as Stop-Start, alternator management and regenerative braking are being introduced by all volume vehicle manufacturers to optimise the use of fuel and energy storage. However, these changes increase the requirements on the battery. Consequently, standard lead acid batteries will no longer do the job. Absorbent Glass Mat (AGM) automotive batteries are needed for these latest Stop- Start technology vehicles.
Stop-Start is designed to save fuel in heavy urban traffic by switching off the engine when a vehicle is stationary. This obviously leads to greater demands on batteries.
Alternator Management monitors a battery’s state of charge during driving and switches off the alternator when the battery reaches its full operating state of charge. Since the alternator typically takes up to 10% of an engine’s power when operating, management of the alternator can give fuel savings depending on the exact conditions of the battery and how the vehicle is driven. The battery supports all the electrical loads on the vehicle during these times, leading again to greater life requirements on the battery.
Regenerative Braking, as the name implies, uses the braking of the car to charge the battery, allowing additional fuel economy as the alternator can be switched off more frequently. This requires the battery to accept current short bursts delivered during braking. In order to optimise recovery of this energy lead-acid battery design had to change to improve charge acceptance ability.
These features, generally called “micro hybrid”, are gradually being adopted into volume manufactured vehicles with 5% of vehicles currently being produced incorporating some or all of these features. They differ from the typical association with the word hybrid seen on vehicles such as the Toyota Prius where the demands on the battery are even higher; meaning more durable (and expensive) battery technologies such as Nickel metal hydride (NiMH) and Lithium-ion (Li-ion) must be employed.
How It Works
AGM batteries are built using a micrometre fine fibre glass mat separator material which stores all battery electrolytes, leaving no free acid within the battery. The clever part of the design is that oxygen formed at the positive plate during overcharging does not leave the cell as in a standard automotive lead-acid battery, but is reduced and reacts with hydrogen produced at the negative plate to form water. These reactions take place within the pores of the separator and mean that the batteries are totally maintenance-free and do not need to carry around an electrolyte “fuel tank” as with conventional lead-acid designs, and do not require top up water for maintenance.
The design benefits of the glass mat over conventional lead-acid batteries enable individual cells within the battery to operate under higher pressures without the fear of squeezing out the acid between the plates which is required for the battery to work. This leads to a step change in durability offered by AGM over conventional lead-acid. The quality of the glass mat is a critical item in ensuring optimum life of the battery in such demanding applications. Laboratory evaluation is boasting four- to fivefold increase in cyclic durability compared with standard designs and typically 16% higher starting power. Increasing surface area and modification to plate designs within the battery improve the engine cranking speed for Stop- Start usage as well as the charge acceptance of the battery for use with regenerative braking.
Benefits of AGM over conventional lead-acid
• Increased lifespan results from battery design – all active materials are retained within the cell enhancing battery longevity
• Higher available power giving faster engine starts
• Totally maintenance-free – zero water consumption
• Spill / leak proof – no free acid within the battery – all held in the glass mat
• Improved efficiency of battery active material, all the acid required by the battery between the plates
AGM automotive batteries require no special tooling to fit to a vehicle and can be charged from existing constant voltage chargers as well as the latest intelligent multi-stage charging systems. Modern automotive battery testers now have an AGM option to enable correct testing and diagnosis of battery condition.
As new micro hybrid vehicles are developed, manufacturers are setting down unique criteria for each vehicle and battery manufacturers are developing batteries for these vehicles on a case-by-case basis. This means that AGM batteries, like engine control units (ECUs) are rapidly becoming vehicle specific.
This has significant ramifications for the vehicle aftermarket as the pace of change is becoming so rapid that current low cost battery manufacturers will not have the time or resources to make the investment needed to produce low cost alternatives. Consequently, the trade will need to align itself with the major OEM battery manufacturers in order to ensure they continue to have the product and the know-how required to replace these increasingly complex parts.
GS Range Overview
GS provides a complete range of automotive batteries covering:
AGM Start Stop Plus (5 part numbers)
EFB Start Stop (8 part numbers)
SMF Conventional (28 part numbers)
MF Conventional (4 part numbers)
Cargo Heavy Duty HD (22 part numbers)
Cargo Super Heavy Duty SHD (8 part numbers)
Leisure (6 part numbers)
Marine (3 part numbers
Garden (5 part numbers)
Specialist (13 part numbers) – for the Honda Jazz I & II, Mazda MX5, Toyota Prius, Nissan Skyline R33/34, iMiev, C-Zero, Ion